In current practice, measurements of single phase flow are made using ultrasonics, such as Doppler shift in liquids which carry suspended solid particles, and various types of spinners, such as gas flow gauges. Two phase liquid flow can also be measured by using ultrasonics, such as Controllotron.TM. ultrasonic gauges, to precisely locate the liquid to liquid interface. Intrusive capacitance gauges are also used to identify the composition of a liquid in a pipe. Finally, in prior art, ultrasonics are used to recognize slug flow, such as, a liquid slug in a gas flow or a gas slug in a liquid flow.
U.S. Pat. No. 4,215,567 (Vicek) describes a method and apparatus for testing a production stream comprised of oil, water, and gas flowing through a conduit to determine the percentages of oil, water, and gas in the stream. A sample portion of the production stream is pumped through a sample line into a sample chamber where it is heated and allowed to remain for a retention period to substantially separate the sample portion into oil and water layers. Gas that evolves from the sample portion is vented from the chamber. At the end of the retention period, the sample portion is pumped back through the sample line into the conduit. As the sample portion flows through the same line the oil and water content of the sample and the volume of the sample are measured to determine the oil and water percentages in the sample portion. Also, the volume of the sample portion is measured as it is pumped through the sample line into the sample chamber and by comparing this volume with the volume of the sample portion pumped back into the conduit, the gas-liquid ratio of the sample portion can be determined.
U.S. Pat. No. 3,246,145 (Higgins) describes a system for determining the relative density of a liquid. The system includes a test chamber into which the liquid is introduced for testing purposes. A radioactive source is positioned on one side of the chamber for directing radiation through the chamber by way of the liquid in the chamber, and a radiation detector is positioned on the other side of the chamber for detecting radiation passing through the liquid and the chamber. At least a portion of the walls of the chamber between the source and the detector are of material relatively transparent to low energy radiation. With such structure, the low energy radiation will be allowed to pass freely from the source into the liquid and from the liquid to the detector. An energy discriminator responsive to only a predetermined low energy range is interconnected with the detector, and interconnected with the discriminator is a recorder for recording an indication of the radiation detected within the low energy range.
The problem not answered in prior art is to measure a three phase flow such as the combination of oil, water and gas in a single flowline. To date there is no monitoring device which can perform this function. It is therefore an object of the present invention to provide an apparatus for measuring three phase flow and also for determining the flow regime in the pipe whether it is slug flow, stratified flow or annular flow.